Field of the Invention
The present invention relates to the connection of fittings used in the transport of fluids, including toxic gases and liquids. More particularly, the present invention relates to the connection of fittings having mating glands, wherein misalignment of the glands or of a gasket interposed therebetween can lead to unintentional and often dangerous inaccurate tightening of the mating nuts of the connection, resulting in an over tightened or under-tightened condition and thus under-compression or over-compression of the gland to gasket or gland to gland interfaces, which can result in leakage of the fluids flowing therethrough.
Description of the Related Art
Piping used to transport fluids and gases often include fittings, wherein a sealing gland of the fitting is attached to one end of a segment of fluid piping such as by welding it thereto, and a mating gland is similarly attached to a second segment of fluid piping. The glands are then brought together in facing relationship with the fluid passages thereof aligned, and a fastener such as a female nut surrounding the first gland and rotatable with respect thereto, and a male nut surrounding the second gland and rotatable with respect thereto, are tightly threaded together to form a sealed fluid connection with the male threaded portion received in a threaded recess in the female nut. In some applications, a ring shaped gasket is interposed between the first and second glands before the nuts are connected.
One issue with connecting gland base fittings is ensuring that the connection is sealed by compression of mating sealing parts such as the glands and gasket, but that the nuts are not overtightened and thus the sealing parts are not over-compressed. If the threaded nuts are not tightened sufficiently, the connection may leak. If the nuts are overtightened, the connection can fail, i.e., be or start leaking, due to stress induced in the nuts, the gland, the gasket, or in the piping or in the weld of the piping to the gland attached thereto, or make it difficult to open the fitting without damaging the nuts or gland if the fitting needs to be removed for servicing of a component or equipment to which it is connected.
The fittings are used, as among other applications, to connect gases and liquids used in industrial applications from a gas or liquid source to a use location thereof, such as an industrial machine. These fluids are often corrosive, pyroforic and/or toxic. If the components of the fitting, or the piping welded thereto, are overstressed or over-compressed as a result of overtightening of the nuts, the fitting may leak or cause the adjacent weld to be stressed, leading to stress corrosion cracking of the piping or welded connection. If the nuts are inadequately tightened, the fitting may leak, leading to evacuation of a manufacturing facility, personal injury, and damage to equipment and facility, including the risk of fire.
To ameliorate the incidence of over or under-tightening of the nuts, a paradigm of tightening the nuts together by a certain number of revolutions or fractions of a revolution following “finger tightening” of the nuts to a “finger tight” condition is employed. Finger tightening is considered turning one nut, or both nuts, relative to the other nut to the maximum amount possible using ones' fingers. Thereafter, a hand tool such as a hand held wrench is employed to execute the subsequent number, or fraction of a number, of revolutions of one nut relative to the other. The number of, or fraction of, revolutions following achieving the “hand tight” condition is often specified by the manufacturer of the fitting, or the end user of the connection. However, different individuals have different ideas of what finger tight is, and different abilities to finger apply the torque needed to turn one nut relative to the other, and thus overtightening and under-tightening of the nuts of the connection, with the issues related thereto, continue to occur. Additionally, different individuals may exceed or fail to apply the desired number of turns or fraction thereof specified by the end user after finger tightening is achieved, also resulting in overtightening and under-tightening of the nuts of the connection, with the issues related thereto
To further complicate finger tightening, a gasket is typically disposed between the glands being pulled together by the nuts to form the sealed fitting connection. In this connection, the face of each gland, or a projection from the face of the gland, presses against the gasket, squeezing and compressing the gasket therebetween to form a gland to gasket to gland sealed connection. However, the presence of the gasket can increase the incidence of fittings being under or overtightened. As the glands are brought together by the relative threaded rotation of the nuts, the gasket will be encountered by one or both of the nuts. If the gasket or the glands are slightly cocked within the envelope of the partially connected nuts, or are hung up therein, the nuts can become hard to turn because one or both of the glands are contacting the gasket, but only a portion of the gasket is contacting the glands, resulting in the nuts being perceived as in the finger tight condition. During manufacturing of a fluid-using product, multiple sections of piping are interconnected, and as a result of tolerance stacking and other potential misalignments, the glands may be sufficiently close to thread the nuts together, but remain spaced apart within the envelope of the nuts, or offset within the envelope of the nuts, to the point where the assembler can no longer turn them using their fingers, resulting in a non-finger tight connection at that point. The offset can be radial, i.e. one gland is initially slightly to the side of the other, or the offset can be non-parallelism of the seating faces of the glands, or spaced apart, i.e., where a gap is present between the glands about their circumference which is greater than the thickness of the gasket, or a combination thereof. Thus, although the assembler believes the connection is in a finger tight condition, the subsequent rotation thereof with a wrench by a certain degrees of rotation specified once the connection is hand tight will under-tighten the connection. On the other hand, if the assembler knows that the connection can yield an inaccurate finger tightened condition, they may compensate by increasing the degrees of rotation of the nuts. If the nuts were properly made up finger tight, the fitting nuts will be overtightened when the post finger tightening rotation is performed.